1. Field of the Invention
The present invention relates to an artificial heart pump and especially relates to an artificial heart pump employing an axial-flow turbo pump that pumps the blood.
2. Description of the Related Art
Conventionally, an artificial heart pump which pumps the blood by utilizing the rotation of the impellers is employed as an alternate being used for medical purposes or as an assist pump. An artificial heart pump utilizing a roller pump or a centrifugal pump and an artificial heart pump utilizing an axial-flow turbo pump are provided as the aforementioned artificial heart pump. Among these various types of artificial heart pumps, the artificial heart pump utilizing an axial-flow turbo pump can reduce the size thereof, being compared with the artificial heart pump utilizing a roller pump or a centrifugal pump.
The conventional artificial heart pump utilizing an axial-flow turbo pump has a housing thereof house motor stators, and at the same time, has a rotor being equipped with impellers on the circumference thereof house permanent magnets which react to the motor stators magnetically. As an artificial heart pump that has been described hereinabove, as shown in FIG. 14, such an artificial heart pump is provided as wherein, a rotor 104 being equipped with impellers 105 on the outer circumference surface thereof is installed between fixed bodies 102 and 103 that are fixed to a housing 101; and pivot bearings 106a and 106b are installed to the surfaces where the fixed bodies 102 and 103 face the rotor 104. To be specific, by protruding the centers of the surfaces of the rotor 104 that face the fixed bodies 102 and 103, the pivot bearings 106a and 106b are formed.
In addition, as shown in FIG. 15, by providing the interiors of the fixed bodies 102 and 103 with magnet coils 111 and 112 that generate magnetic force and by providing both ends of the interior of the rotor 104 with permanent magnets 113 and 114 in such a manner as to face the magnet coils 111 and 112, such an artificial heart pump is provided as is equipped with magnetic bearings that support the rotor 104 by magnetic force. In the artificial heart pump shown in FIG. 15, an active magnetic bearing is constructed in a manner that by installing a position sensor 115 to the fixed body 102, the position of the rotor 104 is detected in order to specify the amount of the current of the magnetic coils 111 and 112, so that the rotor 104 will be located at the optimum position.
Moreover, as shown in FIG. 16, such an artificial heart pump is provided as wherein, the fixed bodies 102 and 103 are connected by a fixed shaft 121; and a rotor 122 having a cylindrical shape and rotating along the outer circumference of the fixed shaft 121 is installed; and at the same time, hydrodynamic bearings are constructed by providing a groove to each of the surfaces where the rotor 122 faces the fixed bodies 102 and 103, respectively. To be specific, by having the rotor 122 rotate, the blood flows into minimal gaps being formed by the grooves that are provided to each of the surfaces where the rotor 122 and the fixed bodies 102 and 103 face, respectively, which consequently generates hydrodynamic pressures, thereby preventing the rotor 122 from contacting the fixed bodies 102 and 103 and behaving as a thrust bearing.
However, when the rotor is supported by the pivot bearings 106a and 106b as shown in FIG. 14, abrasion powders are sometimes generated in the pivot bearings 106a and 106b. In addition, because the gaps between the fixed bodies 102 and 103 and the rotor 104 become narrow, there is a possibility that a blood clot may be formed easily or that red blood cells may be destroyed. Moreover, when active magnetic bearings are employed as shown in FIG. 15, non-contact support will be possible, but electric power will be necessary for active control, and in addition, the construction thereof will become complex as well as the equipment will become larger. Furthermore, when the hydrodynamic bearings are constructed as shown in FIG. 16, narrow gaps will be necessary for generating the hydrodynamic pressures, and due to the relevant gaps, there is a possibility that a blood clot may be formed easily or that red blood cells may possibly be destructed.
In order to prevent the above-mentioned problems, the present applicant proposes an artificial heart pump which prevents the rotor from contacting the fixed bodies by passive type of repulsive magnetic bearings, which not only construct the hydrodynamic bearings but also utilize the magnetic force of repulsion balancing the hydro thrust load on the impellers. (See the Patent Literature No. 1.) The artificial heart pump being equipped with the passive type of repulsive magnetic bearings has permanent magnets 131 and 132 installed to each of the rotor 122 and the fixed body 103 having the construction being shown in FIG. 16, as shown in FIG. 17, thereby having the magnetic force of repulsion balancing the hydro thrust load construct the passive type of repulsive magnetic bearings.
Moreover, such an artificial heart pump is provided as wherein, the artificial heart pump is not only supported by the pivot bearings as shown in FIG. 14 but also axially suspended by providing a permanent magnet to each of the fixed bodies at the front end and the back of the rotor and the rotor, respectively. (See the Patent Literature No. 2.) The artificial heart pump being described hereinabove has permanent magnets installed to the locations of the rotor facing two fixed bodies and to the locations of the two fixed bodies facing the rotor, thereby providing two sets of magnetic forces of repulsion to each of the anterior and the posterior locations of the rotor, respectively, which consequently suspends and supports the rotor.
Patent Literature No. 1: Patent Application Laid Open as 2004-346930
Patent Literature No. 2: Patent Application Laid Open as 2004-351213